Grayite is a rare thorium phosphate mineral that typically occurs as small crystals in pegmatitic environments. Due to its radioactive and toxic nature, it is primarily sought after by advanced mineral collectors and researchers studying phosphate species.

Hardness

Mohs

Luster

Resinous

Streak

White

Transparency

Translucent

mineralrarePhosphate Mineral family

Grayite

Hardness: 4
Luster: Resinous
Streak: White
Transparency: Translucent

Is this grayite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch grayite with a known reference. Grayite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Grayite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Grayite typically shows a resinous luster.
4
Match the color range
Compare against the expected color range: white, yellowish, gray.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: small crystals, granular aggregates.

Often confused with

Grayite vs. its common look-alikes — and how to tell them apart in the field.

mineral

Monazite

Mohs 5-5.5

How to tell apart: Monazite is the harder of the two (Mohs 5-5.5 vs. 4).

How to tell apart: Luster reads resinous on Grayite and vitreous on Xenotime.

Compare →

Often found alongside grayite

Minerals reported to co-occur with grayite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (Th,Pb)PO₄·H₂O
Mohs hardness: 4
Density: 5.0-5.2 g/cm³
Colors: White Yellowish Gray
Streak: White
Luster: Resinous
Transparency: Translucent
Crystal system: Tetragonal
Crystal habit: Small Crystals, Granular Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find grayite

Classic worldwide localities

Congo
Brazil
Norway

Field-hunting tip

Look in pegmatites country — that is the host setting where grayite typically forms. If you start seeing monazite, xenotime, uraninite in float, you are in the right ground. Field specimens usually show a small crystals, granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify grayite?+

Mohs hardness is 4. It typically shows a resinous luster. The streak is white. Common colors include white, yellowish, gray.

Where is grayite found?+

Notable localities include Congo; Brazil; Norway.

How much is grayite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is grayite safe to handle?+

This mineral is radioactive. It contains toxic constituents. Contains thorium, which is radioactive, and lead, which is toxic if ingested or inhaled as dust; handle with care and keep stored in an appropriate lead-lined container or away from long-term exposure areas. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like grayite?+

Grayite is most often confused with Monazite, Xenotime. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with grayite?+

Grayite commonly co-occurs with Monazite, Xenotime, Uraninite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does grayite form in?+

Grayite typically forms in pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is grayite used for?+

Grayite is used in collector, scientific research.

Find grayite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.